1. Field of the Invention
The present invention relates to an image projection system and an image projection method.
2. Description of the Related Art
A conventional optical printing device produces a three-dimensional printing object by use of a photocurable resin in a liquid state having a property of being cured by being irradiated with light such as visible light, ultraviolet light or the like. Such an optical printing device uses, for example, a suspension stacking system, by which a three-dimensional printing object is produced by stacking layers of a photocurable resin cured into a predetermined shape. By the suspension stacking system, a three-dimensional printing object is produced as follows. A light-transmissive plate is provided on a bottom surface of a container that accommodates a liquid photocurable resin in a liquid state, and a bottom surface of the light-transmissive plate is irradiated with light directed from below the light-transmissive plate. The photocurable resin is cured by a predetermined thickness on a printing object holding plate located in the container to forma cured layer. Next, the cured layer is peeled off from the light-transmissive plate, and the printing object holding plate is raised by a predetermined thickness. Then, the photocurable resin is irradiated with light directed from below the light-transmissive plate to form another cured layer, and the newly cured layer is stacked on the first cured layer. Such a process is repeated to stack cured layers, and thus a three-dimensional printing object is produced.
In such an optical printing device, predetermined image data is output from a controller to a projector in order to cure the photocurable resin accommodated in the container into a desired shape. The projector projects a predetermined image to an interface between the bottom surface of the container and the photocurable resin based on the image data. According to an existing image projection system, one cross-sectional image of a three-dimensional printing object is formed by two images projected to an image projection area by two projectors. The image projection area is divided into areas each having a predetermined area, and images are respectively projected to the divided areas by different projectors. Hereinafter, an image projected to such a divided area will be referred to as a “divided image”, whereas an image projected to the entirety of the image projection area and including a plurality of divided images will be referred to as a “large image”.
An example of projection of a large image will be described. For example, an image of “A” is projected to an image projection area having a width of 121 mm (6862 pixels) and a length of 136.1 mm (7716 pixels) by the following method using two projectors each capable of projecting an image of 1366×768 pixels. First, as shown in FIG. 21A, the image projection area is divided into an area S1, which is above the center line in a length direction (vertical direction), and an area S2, which is below the center line. The area S1 is set as an area to which a first projector is to project an image, and the area S2 is set as an area to which a second projector is to project an image. Next, as shown in FIG. 21B, the image of “A” to be projected to the image projection area is divided into a divided image P1 to be projected to the area S1 and a divided image P2 to be projected to the area S2. The divided image P1 is set as an image to be projected by the first projector, and the divided image P2 is set as an image to be projected by the second projector. Then, the divided image P1 is projected by the first projector to the area S1, and the divided image P2 is projected by the second projector to the area S2. Thus, the image of “A” is projected to the entirety of the image projection area.
However, with this image projection system, it is required to adjust the position or the posture of each of the projectors in order to appropriately project the divided images to the areas. The expression “appropriately project” refers to that the divided images are projected by the projectors without being distorted. A technology for adjusting the position or the posture of a projector is disclosed in, for example, Japanese Patent No. 4002983. This publication discloses providing a mechanism that adjusts the position or the posture of a projector.
However, provision of such a mechanism that adjusts the position or the posture of a projector increases the size of the image projection system. This increases the size of the entirety of the optical printing device including the image projection system mounted thereon, and also raises the production cost of the optical printing device. In this situation, an image projection system capable of performing appropriate projection without a mechanism as described above has been desired, but has not been developed so far.